190 LETTERS ON NATURAL MAGIC. 



one, and the other two cylindrical ones of dif- 

 ferent diameters. On the extremities of these 

 rods are fixed small quicksilvered glass beads, 

 either singly or in groups, so that when the in- 

 strument is placed in the light of the sun or in 

 that of a lamp, bright images of the sun or flame 

 are seen reflected on each bead. If any of these 

 rods is set vibrating, these luminous images will 

 form continuous and returning curve lines in a 

 state of constant variation, each different rod 

 giving curves of different characters, as shown 

 in Fig. 44. 



The Melodion, an instrument of great power, 

 embracing five octaves, operates by means of the 

 vibrations of metallic rods of unequal lengths, 

 fixed at one end and free at the other.* A nar- 

 row and thin plate of copper is screwed to the 

 free extremity of each rod, and at right angles to 

 its length ; and its surface is covered with a small 

 piece of felt, impregnated with rosin. This nar- 

 row band is placed near the circumference of a 

 revolving cylinder, and, by touching the key, it 

 is made to descend till it touches the revolving 

 cylinder, and gives out its sound. The sweetness 

 and power of this instrument are unrivalled ; and 

 such is the character of its tones, that persons of 

 a nervous temperament are often entirely over- 

 powered by its effects. 



The vibrations of plates of metal or glass of 

 various forms exhibit a series of the most extra- 

 ordinary phenomena, which are capable of being 

 shown by very simple means. These phenomena 

 are displayed in an infinite variety of regular 



* See Edinburgh Encyclopaedia, Art. SCIENCE, Curiosities 

 in, Vol. xvii., p. 563. 



